Field of the Invention
The technical field relates to an apparatus and a method for producing a Group III nitride semiconductor device and to a method for producing a semiconductor wafer. More particularly, the technical field relates to such an apparatus and a method employing plasma and to a semiconductor wafer production method employing plasma.
Background Art
In Group III nitride semiconductors such as GaN, band gaps can be controlled within the range of 0.6 eV to 6 eV by modulating the composition thereof. Thus, Group III nitride semiconductors are applicable to a wide wavelength range from near IR to deep UV and are widely used in light-emitting devices, laser diodes, photo detectors, and similar devices.
Also, Group III nitride semiconductors have a large breakdown electric field and a high melting point. Thus, Group III nitride semiconductors are expected to replace GaAs-based semiconductors; i.e., materials for a semiconductor device which provide high output power for high frequency and high temperature applications. In fact, HEMT devices and the like employing such a Group III nitride semiconductor have been developed.
Group III nitride semiconductors are epitaxially grown through, for example, metal organic chemical vapor deposition (MOCVD). In MOCVD, ammonia gas must be used in a large amount, and a MOCVD furnace must be equipped with an ammonia-detoxification equipment. Furthermore, the consumption of the large amount ammonia imposes high running cost. In MOCVD, a semiconductor layer is formed through a reaction between organometallic gas and ammonia, requiring a growth substrate to be at a high temperature. When the substrate has high temperature, difficulty is encountered in the growth of a high-quality InGaN layer having a high In concentration. In addition, since the thermal expansion coefficient of the growth substrate differs from that of the semiconductor layer, the grown semiconductor layer tends to be bent.
Another technique for the epitaxial growth of a Group III nitride semiconductor is molecular beam epitaxy (MBE). In MBE, a Group III nitride semiconductor can be grown at low growth temperatures. However, the growth rate decreases in the case of RF-MBE employing radical sources. In other words, RF-MBE is not appropriate for mass production. In the case of MBE employing ammonia gas, production cost rises due to the use of a large amount of ammonia gas.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 1999-36078
Meanwhile, there has been developed a plasma MOCVD apparatus employing plasma. Patent Document 1 discloses a plasma MOCVD apparatus, through which magnesium oxide film can be formed (see Patent Document 1, paragraphs [0020] to [0021]). However, high-quality crystalline Group III nitride semiconductor has not been yielded when plasma MOCVD is employed.